In recent years, there has been demand for high performance portable devices that are also aesthetically pleasing. Consequently, because electronics (including integrated circuit or ICs) have been confined to small housings, heat dissipation for these ICs has become an issue. Conventional fans used in computers and other applications generally use impellers to generate air flow for heat dissipation, but forced air impeller fans are impractical for compact, high performance devices due to size, power constraints, and noise. Therefore, small fans using piezoelectric elements have been studied as replacements for conventional forced air impeller fans.
Turning to FIGS. 1A through 1D, a piezoelectric fan 100 can be seen. Fan 100 is generally comprised of a piezoelectric element 104 that is secured to a generally rectangular metal sheet 102 and which is driven by alternating current (AC) source 106. As can be seen, piezoelectric element 104 is secured to one end of 102, leaving the opposite end free. When driven by a sine wave from AC source 106 shown in FIG. 1D, the free end of the sheet 102 vibrates (as shown in FIG. 1C). As shown, a piezoelectric fan is structurally simple, which smaller, consumes less power, and is quieter than convention forced air impeller fans.
Fan 100 has a natural frequency or mechanical resonance frequency based on physical characteristics. When an AC voltage from source 106 at a frequency equal to the natural frequency of fan 100 is supplied, the vibrational amplitude of sheet 102 is at a maximum, and when the frequency of the AC voltage from source 106 is a slightly different from the natural frequency of sheet 102, the vibrational amplitude falls off drastically. Therefore, to drive the fan at a high efficiency, the frequency of the AC voltage from source 106 should match the natural frequency of the fan 100.